1. Field of the Invention
This invention relates to a type belt type printer used for an electronic calculator and, more particularly, to an improvement in the mask member for the printer.
2. Description of the Prior Art
FIG. 3 is a plan view showing a general type belt type printer of this sort. A pinion 4 is engaged with the output shaft 3 of an electric motor 2 supported to a frame 1, and the rotation of the pinion 4 is transmitted through a pair of idle gears 5 and 6 to a drive pulley 7. A selection lever 8 is rotatably arranged near the drive pulley 7. The rotation of the drive pulley 7 is stopped by engaging the pawl 9 of the selection lever 8 with the drive pulley 7. An electromagnetic clutch 10 is disposed near the selection lever 8. When the clutch 10 is energized, the selection lever 8 is rotated to engage the pawl 9 with the drive pulley 7.
The drive pulley 7 is disposed at one side of the frame 1, and a driven pulley 11 is disposed at the other side of the frame 1. A type belt 12 in which a number of types 14, 14, . . . are projected at an interval on a belt body 13 is wound, as shown in detail in FIG. 4, on the drive pulley 7 and the driven pulley 11.
A platen 15 supported to the frame 11 is arranged in front of the type belt 12, and a carriage 16 which places a hammer member 17 for pressing the desired type 14 of the type belt 12 of the platen 15 side on the platen 15 is disposed laterally movably by a mechanism (not shown) inside the type belt 12. A pair of mask members 18, 18 for preventing the types 14 of both sides of the desired type 14 from being printed when pressing the desired type 14 of the type belt 12 on the platen 15 by the hammer member 17 are supported in a cantilever state to be disposed between the type belt 12 and the platen 15 at an interval corresponding to one of the type 14 at the right and left sides on the lower end of the carriage 16.
The carriage 16 is returned to a home position in a free state by a spring member 19. A sheet S is supplied by a pinch roller 20 and a sheet feed roller, not shown, between the type belt 12 and the carriage 16. Further, an ink roller 21 for coating the type 14 of the type belt 12 with ink is arranged on the type belt 12 near the driven pulley 11.
According to the construction as described above, the rotation of the motor 2 is transmitted from the pinion 4 through the idle gears 5, 6 to the drive pulley 7 to rotate the drive pulley 7. Thus, the type belt 12 is rotated together with the driven pulley 11. When the electromagnetic clutch 10 is energized, the selection lever 8 is rotated to engage the pawl 9 with the drive pulley 7 to stop rotating of the drive pulley 7, thereby stopping the desired type 14 at the position opposite to the carriage 16. The hammer member 17 is driven in the carriage 16, the type 14 is pressed on the sheet S disposed in front of the platen 15 to transfer the ink coated on the type 14 on the sheet S, thereby finishing the print of first digit. Then, the clutch 10 is deenergized to carry the carriage 16, the abovedescribed operation is repeated for necessary digits to finish to print one row. Then, the carriage 16 is returned to the home position by the spring member 19. The sheet S is fed by one row by the pinch roller 20 and the sheet feed roller (not shown), and is introduced to next row for printing.
Even when multicolor printing in the conventional printer of the construction as described above, a plurality of ink rolls 21 are provided to coat selectively exclusive color types 14 with inks of specific colors to be intended to multicolor print, the inks are mixed by adhering the inks mixed from the mask members 18 to the type 14 in contact of the type 14 with the mask members 18 since the mask members 18 are contacted with all the color types 14 to disable fresh multicolor printing.
Thus, as shown in FIGS. 5(A) and 5(B), a printer in which types 14 projected at an interval on the type belt 12 are disposed inside from the ends 22, 22 (one of which is shown) of the belt body 13 laterally of the belt body 13, a pair of horizontal supports 23, 23 (one of which is shown) projected forward are projected at the upper and lower portions of the carriage 16, and a pair of mask members 18A and 18A (one of which is shown) disposed between the type belt 12 and the platen 15 are bent substantially perpendicularly to the belt body 13 side at an interval at right and left sides at the front ends of the supports 23 is already filed by the same assignee as this invention. In this prior invention, as described in copending U.S. Patent application Ser. No. 090,167 the belt body 13 on mask members 18A, 18A,. . . are arranged to contact the both sides of the types 14a, 14a to hold the types 14a, 14a disposed at both sides of the type 14 pressed on the platen 15 by the hammer member 17.
According to the construction as described above, as shown in FIG. 5(B), when the hammer member 17 is energized to press the end of the hammer member 17 on the back of the desired type 14 of the type belt 12, the types 14a, 14a adjacent to the type 14 are pulled to the type 14 to be printed to press in a direction for approaching the platen 15. Before the type 14 to be printed is pressed on the platen 15, the belt 15 of the types 14a, 14a at both sides are contacted with the mask members 18A to prevent the types 14a, 14a from moving forward. Thus, only the desired type 14 is thereafter moved forward to press it on the platen 15, thereby printing the type 14 on the sheet S on the platen 15.
Such a mask member 18A is not directly contacted with the type 14 of the type belt 12 as described above, but is contacted with the belt body 13 of both sides of the type 14a. Thus, the inks are not possibly mixed through the mask member 18A, thereby freshly multicolor printing.
However, in the prior invention described above, the mask member 18A is extended parallel to the extending direction of the belt body 13 of the type belt 12. Therefore, when the pressing force acting on the hammer member 17 for pressing the desired type 14 on the platen 15 is not large after the belt body 13 of both sides of the type 14a is contacted with the mask member 18A, preferable printing cannot be performed on the sheet S due to the presence of the mask member 18A. Consequently, a problem arises that a large size of pressing member having large pressing force for pressing the hammer member 17 must is required.